Sealed well direct expansion heating and cooling system

Details Sealed well direct expansion heating and cooling system Sealed well direct expansion heating and cooling system

2002-08-02

2003-09-09

Tapolcai, William E. (Department: 3743)

Refrigeration

Utilizing solar energy

C062S260000, C165S045000

Reexamination Certificate

active

06615601

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an improved in-ground/in-water heat exchange means for use in association with any heat pump heating/cooling system utilizing in-ground and/or in-water heat exchange elements as a primary or supplemental source of heat transfer, as well as to improved methods of installing in-ground and/or in-water heat exchange tubing.
Ground source/water source heat exchange systems typically utilize liquid-filled closed loops of tubing buried in the ground, or submerged in a body of water, so as to either absorb heat from, or to reject heat into, the naturally occurring geothermal mass and/or water surrounding the buried or submerged tubing.
Water-source heating/cooling systems typically circulate water, or water with anti-freeze, in plastic underground geothermal tubing so as to transfer heat to or from the ground, with a second heat exchange step utilizing a refrigerant to transfer heat to or from the water, and with a third heat exchange step utilizing a compressor and an electric fan to transfer heat to or from the refrigerant to heat or cool interior air space. Further, water-source heating/cooling systems typically utilize closed-loop or open-loop plastic tubing.
Closed-loop systems, often referred to as ground loop heat pumps, typically consist of a supply and return, ¾ inch to 2 inch diameter, plastic tube, joined at the extreme ends via an elbow, or similar, connection. The plastic tubing is typically of equal diameter, wall thickness, and composition, in both the supply and return lines. The water is circulated within the plastic tubing by means of a water pump. In the summer, interior space heat is collected by an a commonly understood interior compressor and air heat exchanger system, or air handler, and is rejected and transferred into the water line via a refrigerant line to water line heat exchanger. In a similar manner in the winter, heat is extracted from the water line and transferred to the interior conditioned air space via the refrigerant liquid within the refrigerant line being circulated in a reverse direction. Many such systems are designed to operate with water temperatures ranges of about a 10 degree Fahrenheit (“F.”) water temperature differential between the water entering and exiting the heat exchange unit's copper refrigerant transport tubing. Water temperatures are often designed to operate in the 40 to 60 degree F. range in the summer, and in the 25 to 45 degree F. range in the winter with anti-freeze added to the water. If a closed-loop, 1.5 inch diameter, plastic water conducting tubing is installed in a horizontal fashion about 5 or 6 feet deep, in 55 degree earth, about 200 to 300 linear feet per ton of system capacity may be necessarily excavated. If the same closed-loop plastic water conducting tubing is installed in a vertical borehole in 55 degree earth, about 150 to 200 feet per ton of system capacity may be necessarily drilled. Requisite distances are longer for horizontal systems because near-surface temperature fluctuations are greater. However, trenching costs are usually less than drilling expenses. In the horizontal style installation, the plastic tubing loop is typically backfilled with earth. In the vertical style installation, the plastic tubing loop inserted into the typical 5 to 6 inch diameter borehole is generally backfilled with a thermally conductive grout. In either the horizontal or the vertical style installation, a water pump is required to circulate the water through the tubing lines, which are generally of equal diameter in both the supply and return segments.
Open-loop systems, often referred to as ground water heat pumps, typically exchange heat to and from interior conditioned air in the same manner as a closed-loop system, but the water circulation segment differs. In an open-loop system, water is pumped from a supply source, such as a well, river, or lake, is run through the water to refrigerant heat exchanger, and is then rejected back into a well, river, or lake. While open-loop systems can significantly reduce plastic tubing excavation or drilling requirements on a system capacity tonnage basis, if an adequate water supply is available, these systems pose a potential environmental threat since bacteria in the surface water transport tubing can be transferred to, and can infect, the water which is being rejected back into the public water supply.
Direct Expansion (“DX”) ground source heat exchange systems typically circulate a refrigerant fluid, such as R-22, in copper underground or underwater geothermal tubing to transfer heat to or from the ground or water, and only require a secondary heat exchange step to transfer heat to or from the interior air space by means of an electric fan. In DX systems, the exterior heat exchange copper refrigerant tubing is placed directly in the geothermal soil and/or water. Historically, due to compressor operational limitations encountered with traditional DX designs installed at depths beyond 50 to 100 feet, most reverse-cycle DX systems, which operate in both the heating and the cooling modes, have been installed with an array of horizontal heat exchange tubes about 5 feet deep, or in vertical boreholes less than 100 feet deep. These prior limitations can be overcome via utilization of a supplemental refrigerant fluid pump, as disclosed in U.S. patent application Ser. No. 10/073,513, by Wiggs.
While most in-ground/in-water heat exchange designs are feasible, various improvements have been developed intended to enhance overall system operational efficiencies. Several such design improvements are taught in U.S. Pat. No. 5,623,986 to Wiggs, in U.S. Pat. No. 5,816,314 to Wiggs, et al., and in U.S. Pat. No. 5,946,928 to Wiggs, the disclosures of which are incorporated herein by reference. These designs basically teach the utilization of a spiraled fluid supply line subjected to naturally surrounding geothermal temperatures, with a fully insulated fluid return line, as well as improved subterranean heat transfer tubing and system component designs.
Other predecessor vertically oriented geothermal heat exchange designs are disclosed by U.S. Pat. No. 5,461,876 to Dressler, and by U.S. Pat. No. 4,741,388 to Kuriowa. Dressler's '876 patent teaches the utilization of an in-ground spiraled fluid supply line, but neglects to insulate the fluid return line, thereby subjecting the heat gained or lost by the circulating fluid to a “short-circuiting” effect as the return line comes in close contact with the warmest or coldest portion of the supply line. Kuriowa's preceding '388 patent is virtually identical to Dressler's subsequent claim, but better, because Kuriowa insulates a portion of the return line, via surrounding it with insulation, thereby reducing the “short-circuiting” effect. Dressler's '876 patent also discloses the alternative use of a pair of concentric tubes, with one tube being within the core of the other, with the inner tube surrounded by insulation or a vacuum. While this multiple concentric tube design reduces the “short-circuiting” effect, it is practically difficult to build and could be functionally cost-prohibitive.
The problem encountered with insulating the heat transfer return line, by means of fully surrounding a portion of same with insulation as per Kuriowa, or by means of a fully insulated concentric tube within a tube as per Dressler, or by means of a fully insulated return line as per Wiggs' predecessor designs, is that the fully insulated portion of the return line is not exposed to naturally occurring geothermal temperatures, and is therefore a costly necessary underground/underwater system component which is not capable of being utilized for geothermal heat transfer purposes. While the utilization of such fully insulated costly components is an improvement over prior totally un-insulated geothermal heat transfer line designs subject to a “short-circuiting” of the maximum heat gain/loss potential, a design which insulates the supply line from the return li

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